Electronically controlled fluid coupling device with fluid scavenge control and enhanced cooling

ABSTRACT

A viscous fan drive with a front-mounted fan and electrical actuation without a tethered harness. The mechanical package includes an inverted viscous clutch, a drive pulley, a split electromagnetic actuator with the electrical portion mounted to a stationary mounting member. Enhanced cooling can be provided with breather openings in the pulley, breather slots in the body member, and fins in the reservoir.

RELATED APPLICATION

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 11/427,153, filed on Jun. 28, 2006, which in turnis a continuation of U.S. patent application Ser. No. 10/929,801, filedon Aug. 30, 2004, and now U.S. Pat. No. 7,083,032.

TECHNICAL FIELD

The present invention relates generally to viscous fan drive systems,and more specifically to electronically controlled fluid couplingdevices for fan drive systems.

BACKGROUND OF THE INVENTION

The present invention relates to fluid coupling devices, particularly ofthe type having both a fluid operating chamber and a fluid reservoirchamber, as well as valving which controls the quantity of viscous fluidin the operating chamber.

Although the present invention may be used advantageously in fluidcoupling devices having various configurations and applications, it isespecially advantageous in a coupling device of the type used to drive aradiator cooling fan of an internal combustion engine, and will bedescribed in connection herewith. It is to be understood, however, thatthe present invention can be used with other accessories or componentsand in industrial applications, rather than just with vehicles, such asautomobiles and trucks.

Fluid coupling devices of the viscous clutch type, have been used formany years for driving engine cooling fans (thus called “fan drives”).Such fan drives can result in substantial savings of engine horsepowerand thus can increase the amount of miles of travel that the vehicle canachieve per gallon of fuel. The typical fluid coupling device operatesin the engaged, relatively higher speed condition only when cooling isneeded, and operates in a disengaged, relatively lower speed conditionwhen little or no cooling is required.

Electrically activated viscous fan drives are known and used todaybecause they can be precisely controlled between an engaged, partiallyengaged, and disengaged mode to control output at a given fan speed asdetermined by the vehicle's engine computer.

The electrically actuated viscous fan drives in use today have theactuator mounted to either the front or rear sides of the fan drives. Inboth cases, the actuators are mounted to the drives with ball bearingsand the electrical wires are tethered to a stationary location on theengine or shroud or whatever optimum location is appropriate for theparticular vehicle or customer application.

For front-mounted actuators the length of the electrical tether (wireharness) is a limiting factor for large fan applications. Forrear-mounted actuators, the axle length can limit usage in narrowpackage applications. In addition, they also require a tether (wireharness) from the fan drive to a stationary location that can bedifficult to install in the vehicle if the fan is assembled to the fandrive before installation. The durability of either design is a functionof the bearing life as well as the durability and life of the tetheredelectrical wires and/or brackets.

Thus, a fan drive without a tether, that is without electrical wirestethered to a stationary location, and without actuators mounted to ballbearings, could improve the durability of the fan drive, as well aslower the cost of the fluid coupling drive. It is also important,however, that the tetherless fan drive maintain the same or similar fandrive performance characteristics and attributes as the tethered fandrive.

The front-mounted electrical actuator fan drive was the result of anevolution of earlier air-actuated viscous fan drives used in heavy truckand large bus applications. Initially, bi-metal control spring membersand mechanisms were utilized on the front of the viscous drives. Thesewere subsequently replaced by bearing-mounted pneumatic solenoids.Durability issues with the tethers and higher fuel economy requirementsdemanded by the public and government entities forced the heavy-dutyindustry to switch to pneumatic on/off friction clutches without atether. In these clutches, the air supply was supplied through thecenter of the mounting brackets—pulley subassembly.

Today, the automotive and heavy-duty industry is facing even stifferfuel economy restrictions, as well as noise control requirements. Thesecontinue the need for variable speed or at least multi-speed fan drives.As a result, viscous drives are economical and durable solutions thathave evolved to the use of rear-actuated viscous fan drives. Theserear-mounted electrically controlled actuators were developed to reducepotential tether durability problems associated with front-mounted styleactuators.

Front actuated viscous fan drives continued to be used for light tomedium duty applications because the axial length and cost are betterthan rear actuated fan drives. However, in some light duty gasolineengine applications where the fan clutch is driven by the water pump, asystem resonant problem exists caused by numerous factors including themass center of gravity (CG) of the fan drive.

Thus, a new and improved viscous fan drive is needed for numerousapplications, whether for light, medium duty or heavy vehicle usage. Inaddition, the need exists for actuators having reduced costs, improveddurability, and better noise and vibration performance.

SUMMARY OF THE INVENTION

The present invention is intended to minimize the aforementionedproblems and concerns with tethered actuators and system resonanceissues while incorporating desirable features, such as a high-speedreservoir, and a combined “failsafe” and anti-drain back option. Theinvention also utilizes a scavenge control valve configured on a lowspeed member which performs as a fluid flow diverter.

The present invention provides a viscous fan drive with a front-mountedfan and electrical actuation without a tethered harness. The presentinvention utilizes an inverted viscous clutch, a drive pulley, and asplit electromagnetic actuator resulting in a purely mechanical packagethat provides several advantages over existing engine-drivenelectronically managed viscous fan drives. An inverted clutch is onewhere the conventional clutch is essentially flipped around such thatthe central shaft is the output shaft while the outer members, such asthe body and cover, are the input.

In this configuration, the electrical portion of the actuator is notphysically mounted to the fan drive, but rather is mounted to astationary member at the drive pulley. The stationary member could alsobe attached to the water pump housing. The remaining actuator componentsare integral to the fan drive and, as a result, the fan drive itself hasonly mechanical parts. With the embodiment disclosed in the presentapplication, the bearing location, pulley mounting, clutch mounting, fanmounting, and differential speed sensor magnet are all positioned tooptimize performance and application of the viscous fan drive.Embodiments of the invention can use high speed reservoirs withaccumulators, scavenge control with a low speed valves, stamped metalcovers, and integrated slip speed sensors. The invention allows for fastresponse times for engagement or disengagement of the clutch and alsoallows for open-loop control of electrical actuation.

Other benefits, features, and advantages of the present invention willbecome apparent from the following description of the invention, whenviewed together with the accompanying drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 an exploded view of an embodiment of the present invention.

FIG. 2 is a perspective partial cross-sectional view of a viscous fandrive in accordance with an embodiment of the present invention.

FIG. 3 is a cross-sectional view of an embodiment of the presentinvention.

FIGS. 4A-B illustrate the engaged and disengaged positions,respectively, of the valve assembly in accordance with an embodiment ofthe present invention.

FIGS. 5A-5D illustrate components of a slip speed sensor and theoperation thereof in accordance with an embodiment of the presentinvention.

FIG. 6 is a schematic illustration of a check valve mechanism which canbe used with an embodiment of the present invention.

FIGS. 7A-7C and 8 illustrate other embodiments for aiding the cooling ofa fan drive system in accordance with embodiments of the presentinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to the drawings, which are not intended to limit theinvention, FIGS. 1-3 illustrate one embodiment of a fluid couplingdevice 10 (“viscous fan drive”) in accordance with the presentinvention. The device 10 includes a viscous drive mechanism 12 which isutilized to control the speed of rotation of a cooling fan 14. Theviscous drive mechanism 12 is attached to a pulley 16 which is operatedby a belt (not shown) on the front of a vehicle engine. The fan drive isactivated electrically by an electrical coil 18 which is fixedly mountedto a stationary mounting member 20. The mounting member 20 can be abracket attached to a vehicle engine or the like, or a mounting bracketfor a vehicle water pump. A portion of a water pump 22 is shown, forexample, in FIGS. 1-3.

The fan member 14 can be any type of fan member known and used today,such as a plastic or metal fan. The fan member 14 is mounted by aplurality of fasteners, such as bolts 15 directly to the rotor member 34and rotates with it.

The viscous drive mechanism includes a cover plate member 30, a bearingmember 32, a rotor member 34, an armature member 36, a reservoir platemember 38 and a body member 40. The body member 40 has a plurality ofexternal fin members 100 which are used to help cool the cover memberand the internal components and fluid within the viscous fan drive. Therotor member, reservoir plate member and body member are preferably madefrom an aluminum material. The cover plate is preferably made from ametal material such as steel and stamped into the configuration shown inthe drawings. A stamped steel cover plate is less expensive than a diecast cover member with fins which is conventionally used in viscous fandrives today. The armature member 36 is preferably made from a plasticmaterial.

Also, as shown in FIG. 3, the cover plate member 30 is fixedly securedto the body member 40. This can be accomplished by a portion of the bodymember being deformed and swaged over the edge of the cover member, asshown by reference number 31. The body member in turn is directlyattached to the pulley member 16 by a plurality of bolts or otherfasteners 47.

A rotary seal 42 is used to seal the joint between the cover platemember 30 and the body member 40 to prevent leakage of the viscous fluidadjacent the fan member 14.

A mounting bolt 44 together with a washer 46 (also known as “slinger”),are used to mount the viscous drive mechanism 12 and pulley member 16 tothe mounting member 20. The mounting bolt 44 fits within a hollow shaftmember 48 which is mounted on the end 49 of the rotating shaft 50, whichin this example is a water pump shaft.

The shaft 50 is rotatable mounted within the stationary mounting member20 by bearing members 52 and 54. The mounting bolt 44 is threadedlymounted to the rotating shaft 50 as shown in FIG. 3.

The electromagnetic system utilized with the viscous fan drive mechanismincludes a coil 18, along with a steel housing member 19, both of whichare mounted to the stationary mounting member 20. The coil 18 has a wireharness 60 that is electrically coupled to a controller 62 and a powersource 64. The controller 62 receives electrical signals from aplurality of engine sensors 66 regarding engine and vehicle operatingconditions. The operating conditions could be engine temperature, fueleconomy, emissions or other engine operating conditions affecting theperformance of the engine. For example, one of the sensors 66 could bean engine mounted coolant sensor or a pressure sensor mounted to the airconditioner. The controller 62 has a stored look-up table thatdetermines a desired engine operating range for a given engine speed.When the controller 62 determines that one of more of the sensors 66 aresensing cooling conditions outside the desired operating range, theexternal controller 62 will direct the power source 64 to sendelectrical power to the coil 18 as a function of this electrical signal.Thus, for example, if the external controller 62 determines that theengine coolant temperature is too low, or that the engine temperature istoo low, a signal may be sent from the controller 62 to the power source64 to activate the coil 18 to its desired pulse width, therein providinga magnetic field within the fluid coupling device 10.

Similarly, if the external controller 62 determines from one or more ofthe sensors 66 that the engine, or engine coolant temperature, is abovean undesired high range, no signal is sent to the external controller 62to the power source 64 and coil 18. Thus, in this manner, the controller62 interprets the signals from the sensor to direct the power source 64to send or not send electrical current to the coil 18 via the wireharness 60 to control the output from the viscous fan drive 10 in amanner described herein.

As indicated, the stationary mounting member 20 can include a water pumpshaft 50 mounted directly to an engine block (not shown) near the crankshaft pulley (not shown) using bolts or other conventional fasteners. Inan alternative embodiment (not shown), the water pump mounting bracketcan be a stand-alone bracket-pulley subassembly. The water pump shaft 50is coupled to a plurality of impellers 23 used to control engine coolantflow within an engine cooling system to cool the engine. The water pumpshaft 50 is mounted to the pulley 16 through the hollow shaft member 48.Thus, the shaft member 50 rotates at the same rotational rate as thepulley 16 to drive the impellers and therein provide coolant flow to theengine.

As indicated, the pulley 16 is coupled to the engine crankshaft by adrive belt (not shown) and rotates the body member 40 at a ratedetermined by the engine operating speed translated to the pulley 16through the crankshaft and belt. The body member 40, which is preferablymade from a die cast aluminum material, has an overlying region 31 thatis used to hold the stamped cover plate member 30 fixedly in place inthe viscous fan drive. Thus, the body member 40 and the cover plate 30rotate at the same rotational rate as the pulley member 16.

The fan member 14 is rotatably mounted within the viscous fan driveusing the ball bearing member 32 and is fixed to the rotor member 34.The rotor member and fan member thus comprise the output of the viscousfan drive.

The volume of space around the rotor member 34 and bounded by the cover30 and body member 40 defines a fluid reservoir 70 in which a quantityof viscous fluid is provided (not shown). The cover member 30 andreservoir plate 38 define a fluid chamber 72. The volume of spacebetween the radially outer portion of the rotor member 34 and the bodymember 40 defines the fluid working chamber 74 for the viscous fandrive.

The fluid reservoir 70 is fluidically coupled with the fluid chamberupon movement of the armature member 36 in a manner to be describedbelow. The axial movement of the armature member opens and closes ascavenge fluid flow path depending upon actuation of the electrical coil18 which controls the flow of fluid between the fluid reservoir andfluid chamber. In addition, the fluid chamber 72 is fluidically coupledto a working chamber 74 which is defined between the outer ends of therotor member in combination with the body member 40 and cover member 30in a conventional manner. The amount of viscous fluid contained in theworking chamber 74, in conjunction with the rotational speed of thecover and body members coupled to the pulley member 16, determines thetorque transmitted to the rotor member 34 that rotates the fan member14. In other words, the torque response is a result of viscous shearwithin the working chamber 74. Thus, as indicated, the rotation of thefan member is used to cool the radiator or other engine components asrequired by the engine controller and the appropriate sensors.

The armature member 36 is preferably made from a plastic material andhas a metal armature ring 37 attached to its outside circumference.(This is better shown in FIG. 5B.) The armature ring 37 is made from aferrous material. In addition, a multi-pole ring magnet 43 is attachedto and part of the armature member 36. The armature ring and multi-polering magnet act in combination with the electromagnetic circuitry causedby the coil member 18 to move the armature member in an axial directionalong the longitudinal axis of the viscous fan drive system. In thisregard, the longitudinal axis is indicated by the centerline 51 (FIGS.3, 4A, 4B and 5A).

The hub member 39 is made from a ferrous or metal material and is insertcast molded into the body member 40. The hub member has a conical shapewith a U-shaped cross-section as shown, in particular, in FIGS. 3 and4A-4B. After the body member is cast with the hub member in it, anannular channel 53 is formed in the hub member. The channel 53 is inaxial alignment with the armature ring 37 on the armature member 36. Thespace formed by the annular channel 53 provides a working gap in whichthe armature ring is pulled into and positioned upon actuation of theelectromagnetic system in accordance with the present invention.

The armature member 36 is essentially a valve member and operates toopen and close the scavenge fluid flow path of the viscous clutchmechanism. This is shown more particularly in FIGS. 4A and 4B. FIG. 4Adepicts the valve member in the engaged position and FIG. 4B illustratesthe valve member in the disengaged position. In the disengaged position,an opening 80 is provided between the armature member 36 and thereservoir plate member 38 allowing the scavenge fluid flow path to openand the viscous fluid 77A to flow back into the reservoir chamber 70.This disengages the fan member. In the engaged position, the workingchamber 74 is filled with viscous fluid and the output members, namelythe rotor member 24 and fan member 14, are rotating at full speed orcapacity and providing full cooling to the radiator or other engineaccessories as needed. In this operational position, the opening 80 isclosed and the viscous fluid 77B which is scavenged from the workingchamber 74 through scavenge channel 75 to the fluid chamber 72 isrecirculated to the working chamber 74.

As a result of the manner in which the fan member is engaged anddisengaged, the viscous fan drive is normally in the “on” position. Thisis known as the “failsafe” condition. In addition, the amount by whichthe armature member 36 is moved axially and the corresponding amountthat the opening 80 is opened regulates the amount of viscous fluidwhich is returned to the fluid reservoir and the amount which isrecirculated to the working chamber. This regulates the speed of the fanmember. Thus, with the present invention, the fan member can be in the“on” condition, the “off” condition, and at any rotational speed betweenthose two conditions.

It is also possible with an alternate embodiment of the presentinvention to provide a viscous fan drive which is always in the “off”position and the fan member is only engaged when electrical power isprovided and the electromagnetic circuitry is activated. This could beprovided with the same structure and components as the failsafeembodiment, but would entail a modification of the programming in thecontroller 62.

As indicated, the rotor member 34 has a scavenge tunnel 75 whichoperates in the same manner as scavenge tunnels with rotor members ofconventional viscous fan drives and provides a return path for theviscous fluid from the working chamber back into the fluid chamberand/or fluid reservoir.

The flux path for the electromagnetic circuitry is shown by arrows A inFIG. 4B. The flux path A includes the ferrous hub member 39 and theferrous housing member 19. As indicated, when the sensors 66 indicate tothe controller 62 that the rotation of the fan member is not desired ornot desired to the same extent, then the coil member 18 is actuated. Theactuation of the coil member creates the flux path A, which due to themulti-pole ring magnet 43, moves the armature member axially andpositions the armature ring 37 into the channel (or “working gap”) 53.

The present invention has numerous advantages over other viscous fluidfan drive mechanisms and systems. Without the tethered wire harness,there are fewer electrical inner connections necessary. Also, the coilmember and electrical circuitry is more easily serviceable. The slipheat capacity is improved due to the rotation of the cover member withits cooling fins at input speed which also provides additional fluidreservoir cooling. The invention also has a failsafe mode and isnormally in the engaged or “on” condition and also has a quiet startup.The reaction time for the pump out and fill of the working chamber areimproved since the scavenge rate is independent of the fill rate.

The scavenge flow control valve is also part of the output member whichthus reduces dynamic loading effects on the valve member. The inventionalso enables “smart” controller integration since the electronics arenot physically connected to the fan drive.

The invention also has a smaller number of components then tetheredviscous fan drives. The present invention has as much as 30 percentfewer components than corresponding tethered viscous fan drives, eitherfront mounted or rear mounted. This provides lower cost and improvedreliability of the viscous fan drive mechanism and system. Also,warranty costs could be reduced since the electronic components are moreserviceable and fewer components are needed.

The viscous fan drive mechanism in accordance with the present inventionis also easier to assemble to the vehicle. Further, with the presentinvention, the axial length of the viscous fan drive mechanism isreduced, as much as 50-60 millimeters. This can be important in vehicleswhich have limited space in the engine compartment. In addition, thescavenge control utilizes a low speed valve mechanism which is a benefitand improvement over prior viscous fan drive systems.

One embodiment of the present invention also utilizes an integrated slipspeed sensor. A preferred sensor of this type is shown, for example, inU.S. patent application Ser. No. 60/806,638, filed Jul. 6, 2006, thedisclosure of which is hereby incorporated herein by reference. Theintegrated slip speed sensor monitors the clutch output speed with anelectromagnetic circuit partially comprised of components common withthe clutch. The circuit configuration provides a speed sensor thatmeasures the speed differential between the clutch output and the clutchinput. When measured by the controller (or a remote computer), thedifferential speed is subtracted from the clutch input speed todetermine the output speed.

For the electromagnetic circuit, a sensor pole member 41 is provided,along with a Hall Effect Device (HED) 110, or another magnetic sensingdevice. The HED 110 is positioned on the end of a flux concentrator 111which is attached to the coil member 18. There are shown moreparticularly in FIGS. 5C and 5D, in combination with FIG. 5A whichdepicts the flux path B of the slip speed sensor system. The pole member41 has a plurality of magnetic poles 112 arranged circumferentiallyaround the inside of an outer ring 114. The flux path B includes the HEDsensor 110, the hollow shaft member 48, the ring magnet 43, the polemember 41 and the hub member 39.

The ring magnet pole member 41 rotates at input speed relative to thestationary HED 110. The alternating poles of the ring magnet 41 createalternating directions of the magnetic flux in the magnetic circuitproportional to the differential speed of the input and output. Thedifferential speed is determined by the difference in speed between thepole member 41 and ring magnet 43.

Another feature of one embodiment of the present invention is theimproved manner in which the viscous fluid and the viscous valvemechanism is aided in being cooled. As indicated, the body member 40 isa cast metal component, preferably made from an aluminum material, andhas a plurality of fin members 100 cast on the outside surface. This isshown in particular in FIG. 7B. In addition, the body member rotates atinput speed since it is directly coupled to the pulley member 16. Theviscous fluid reservoir in turn rotates at the same input speed. Thefluid reservoir is thus similarly connected to the cooling fins of thebody member with the present invention and is maintained at a lowertemperature by the effect of the cooling fins.

A plurality of openings 120, called “breather” openings, in the pulleymember, as shown in FIG. 7A, assist in allowing air flow to more easilypass over the cooling fins. As shown in FIG. 7A, four enlarged openings120 are provided and the air flow is depicted by arrows 115. It isunderstood that any size and number of openings can be provided,however, so long as the strength and durability of the pulley member arenot compromised. Also, the larger the openings or the larger area ofopen space in the pulley member, the greater the cooling effect.

In addition, in order to space the pulley member 16 from the body member40 and to minimize conduction of heat from the body member to the pulleymember, raised bosses 130 are provided at each of the mounting openings132 where the pulley member is attached to the body member by bolts 47or other fasteners. This is shown in FIG. 7B. The raised boss members130 can be positioned either on the body member 40, as shown in FIG. 7B,or on the pulley member 16′ as shown in FIG. 8 as boss members 130′.This minimizes the conduction of heat from the body member to the pulleymember and vice versa.

In addition, as also shown in FIG. 7B, a plurality of grooves or slots140, also called “breather” slots, are provided on the outside surfaceof the body member 40 aid in allowing air flow over the cooling fins100. The air flow passes through the breather openings 120 in the pulley16 and through the breather slots 140 in the body member 40. This allowsthe air flow to contact more of the surface of the cooling fins 100,thus aiding in cooling.

In addition, as shown in FIG. 7C, a number of fin members 150 areprovided inside the reservoir chamber 70. The fin members 150 can beformed and provided by the breather slots 140 in the exterior surface ofthe body member 40. The fins 150 inside the viscous fluid reservoir alsoaid in the heat transfer of heat from the viscous fluid to the coolingfins 100 and thus to the atmosphere inside the engine compartment of thevehicle.

Another feature of the inventive viscous fan drive system is shown inFIG. 6. In this embodiment, a check valve 90 can be utilized. The checkvalve 90 prevents drain back and reduces residual channel fluid. Thecheck valve has a spring actuated piston member 92 biased by springmember 94 against a plug member 95. The plug member 95 is positioned inthe channel or bore 96 (after the bore is formed) in order to hold thepiston member and spring member in position. The channel member 96 hasassociated secondary scavenge channel member 97 which is in directcommunication with the reservoir chamber 70. The channel 96 also has anassociated channel member or passageway 98 which is in directcommunication with the working chamber 74. The check valve mechanism 90improves the response and controllability of the viscous fan drive. Itprovides a shorter fill path which improves controllability due toreduced fluid fill lag time. The wiper is essentially “inverted” andimproves the fill rate as well. The check valve mechanism 90 preventsdrain back and reduces residual channel fluid.

In operation, with a check valve mechanism 90 positioned in the bodymember 40 which is rotating at input speed, the centrifugal force on thepiston member 92 forces the piston member outwardly against the plugmember 95 and against the force of the spring member 94. In thiscondition, there is a direct flow path through channel members 98 and 97from the working chamber to the fluid reservoir. Thus, when the viscousdrive mechanism is in the engaged position and the fan member isrotating, there is a continuous flow of fluid from the reservoir to theworking chamber and back to the reservoir.

When the engine is turned off or not in operation, the spring member 94biases the piston member 92 in a radially inward position as shown byarrow member 99 in FIG. 6. The piston member 92 closes the end of thechannel or passageway 98 thus preventing the viscous fluid from drainingfrom the fluid reservoir into the working chamber. This aids inproviding a quieter startup of the engine.

With fewer components, the viscous fan drive in accordance with thepresent invention has less weight and less overhanging mass. The lighterweight can help improve fuel economy of the vehicle, while the less massthat overhangs the mounting member can improve the durability of thebearings and shaft member for the water pump or other associatedcomponent.

The rotor member 34 also includes a scavenge system that returns viscousfluid from the working chamber to the reservoir chamber in aconventional manner. Disposed adjacent the radially outer periphery ofthe working chamber is a pumping element also referred to as a “wiper”element (see 105 in FIG. 7C). The wiper element operates to engage arelatively rotating fluid in the operating chamber and generate alocalized region of relatively higher fluid pressure. As a result, asmall quantity of fluid is continuously pumped from the working chamberback into the reservoir chamber through a scavenge channel, such aschannel 75 in the drawings.

The amount of electrical power supplied in terms of pulse widthmodulation from the external controller 62 and power source 64 enhancethe amount of magnetic flux available to control the relativepositioning of the axially movable armature valve member 36. Asindicated, the controller receives a set of electrical inputs fromvarious engine sensors 66 that monitor various engine operatingconditions. The lookup table in the controller determines a desiredengine operating range for a given engine speed. When input from one ofthe sensors to the controller indicates that cooling conditions areoutside the desired operating range, the external controller 62 willdirect the power source 64 to send electrical power to the coil member18 as a function of this electrical signal. Thus, for example, if thearmature member is pulled or moved axially, a gap is opened between thearmature member 36 and the reservoir plate 38 allowing viscous fluid toreturn to the reservoir 70. This in turn reduces the amount of viscousfluid in the working chamber. Hence, a fan coupled to the output memberwould rotate slower.

Similarly, if the external controller 62 determines from one or more ofthe sensors 66 that the engine, or engine coolant temperature, is abovean undesired high range, no signal is sent from the external controller62 to the power source 64 and coil 18. The armature valve member 36 isthus maintained in a position wherein the gap 80 is closed allowingmaximum fluid flow from the fluid reservoir 70 to the fluid chamber 72and to the working chamber 74. This provides maximum torque response ofthe rotor 34 which in turn rotates the fan member 14 to provide maximumcooling to the radiator to cool the engine coolant.

The present invention provides numerous advantages over currentlyavailable front and rear actuated viscous fan drives. For example, theelectrical portion of the actuator is not physically attached to the fandrive, but rather is mounted to a stationary member of the drive pulley.As such, there is no tethered wire harness and no actuator bearing. Thisleads to easier and less costly manufacturing, as there are no wires orconnectors. Further, the coil is easily replaced, which lowers serviceand warranty costs.

Further, the remaining actuator components are integral with the engineside of the fan drive. This leads to lower overhanging mass on the drivecomponents, which leads to higher system resonant frequency and possibleimprovements in waterpump or component durability. This also leads tocompact packaging, which can improve vehicle costs.

Finally, in another embodiment, the amount of pulse width modulation tosaid electrical coil could be such to generate a magnetic field in whichthe armature valve member 36 partially covers the gap 80. The magneticfield generated would be less than the magnetic field necessary toaxially translate the armature valve member completely to the secondposition completely opening the annular gap 80. This position wouldallow partial engagement of said rotor 34 and output at an infinitenumber of midlevel outputs to more precisely control the amount ofcooling available to the radiator.

While preferred embodiments of the present invention have been shown anddescribed herein, numerous variations and alternative embodiments willoccur to those skilled in the art. Accordingly, it is intended that theinvention is not limited to the preferred embodiments described hereinbut instead limited to the terms of the appended claims.

1. A fluid coupling device comprising: an output member; an input memberrotating about and engageable with said output member, said input memberrotating at an input speed; said input member comprising a body memberand a cover member coupled to said body member; a working chamberdisposed between and at least partially defined by said input member andsaid output member; and a pulley member attached to said input member;said output member engageable with said input member through receptionof fluid within said working chamber; said pulley member having at leastone opening to allow cooling air to pass through and assist in coolingsaid input member; and said body member having a plurality of outer finmembers and a plurality of breather slots in the outer surface to assistin directing cooling air against said fin members.
 2. A fluid couplingdevice as in claim 1 wherein said input member is configured forattachment to a water pump, said input member rotating at the same speedas said water pump.
 3. A fluid coupling device as in claim 1 whereinsaid output member is configured for attachment to a fan.
 4. A fluidcoupling device as in claim 1 further comprising at least one valve,said at least one valve controlling engagement of said output memberwith said input member.
 5. A fluid coupling device as in claim 1 whereinsaid input member in rotating at an input speed rotates at an engineinput speed.
 6. The fluid coupling device as in claim 1 wherein saidpulley member has a plurality of openings to allow cooling air to passthrough.
 7. The fluid coupling device as in claim 1 wherein said bodymember has a plurality of raised boss members in order to space saidpulley member from said body member.
 8. The fluid coupling device as inclaim 1 wherein said pulley member has a plurality of raised bossmembers in order to space said pulley member from said body member. 9.The fluid coupling device of claim 1 further comprising a rotor member,a reservoir plate member and a moveable valve member.
 10. The fluidcoupling device of claim 9 wherein said reservoir plate member has anannular fluid aperture which is adapted to be covered, uncovered orpartially covered by said axially moveable valve member.
 11. The fluidcoupling device of claim 9 wherein said reservoir plate member and saidbody member define a fluid reservoir chamber for viscous fluid, andwherein said body member has a plurality of fin members protruding intosaid fluid reservoir chamber.
 12. A fluid coupling device comprising: anoutput member; an input member rotating about and engageable with saidoutput member, said input member rotating at an input speed; said inputmember having a body member and a cover member; a working chamberdisposed between and at least partially defined by said input member andsaid output member; and a pulley member attached to said input member;said output member engageable with said input member through receptionof fluid within said working chamber; said pulley member having at leastone opening to allow cooling air to pass through and assist in coolingsaid input member; a rotor member, a reservoir plate member and amoveable valve member; said reservoir plate member having an annularfluid aperture which is adapted to be covered, uncovered or partiallycovered by said moveable valve member; and said reservoir plate memberand said body member defining a fluid reservoir chamber for viscousfluid, and wherein said body member has a plurality of fin membersprotruding into said fluid reservoir chamber.
 13. The fluid couplingdevice of claim 12 wherein said body member has a plurality of outer finmembers and a plurality of breather slots, said breather slots assistingin directing air toward said fin members.
 14. A fluid coupling devicecomprising: an output member; an input member rotating about andengageable with said output member, said input member rotating at aninput speed; said input member having a body member and a cover member;a working chamber disposed between and at least partially defined bysaid input member and said output member; and a pulley member attachedto said input member; said output member engageable with said inputmember through reception of fluid within said working chamber; saidpulley member having at least one opening to allow cooling air to passthrough and assist in cooling said input member; and a rotor member, areservoir plate member and a moveable valve member; said reservoir platemember and said body member defining a fluid reservoir chamber forviscous fluid and wherein said body member has a plurality of finmembers protruding into said fluid reservoir chamber.
 15. A fluidcoupling device comprising: an output member; an input member rotatingabout and engageable with said output member, said input member rotatingat an input speed; said input member having a body member and a covermember; a working chamber disposed between and at least partiallydefined by said input member and said output member; and a pulley memberattached to said input member; said output member engageable with saidinput member through reception of fluid within said working chamber;said pulley member having at least one opening to allow cooling air topass through and assist in cooling said input member; a rotor member, areservoir plate member and a moveable valve member; said reservoir platemember having an annular fluid aperture which is adapted to be covered,uncovered or partially covered by said moveable valve member; andwherein said body member has a plurality of outer fin members and aplurality of breather slots, said breather slots assisting in directingair toward said fin members.
 16. A fluid coupling device comprising: anoutput member; an input member rotating about and engageable with saidoutput member, said input member rotating at an input speed; said inputmember having a body member and a cover member; a working chamberdisposed between and at least partially defined by said input member andsaid output member; and a pulley member attached to said input member;said output member engageable with said input member through receptionof fluid within said working chamber; said pulley member having at leastone opening to allow cooling air to pass through and assist in coolingsaid input member; said body member having a plurality of outer finmembers and a plurality of breather slots in the outer surface to assistin directing cooling air against said fin members; and said pulleymember having a plurality of raised boss members in order to space saidpulley member from said body member.